Field of the Art
The disclosure relates to the field of telephony, and more particularly to the field of quality of experience.
Discussion of the State of the Art
Audio system measurements are instrumental to operating and maintaining a reliable telephony network. Measurements may help in sizing and specifying new equipment or monitoring or troubleshooting existing equipment. Audio system measurements typically model psychoacoustic principles to assess the quality of a communication system as it may pertain to human hearing. In telephony systems, a Mean Opinion Score (MOS) provides a numerical indication of quality of speech as perceived by the listening end of the communication, and while it is subjective, MOS tests have been standardized and are specified by the International Telecommunications Union, ITU-T, under published recommendation P.800.
A Mean Opinion Score (MOS) is a type of quality measurement test that has been used for decades in telephony to obtain a human user's perceived quality of a voice call or audio file played over the given telephony network or system. Initially, a Mean Opinion Score is recorded by each listener as an integer in a range of 1 to 5, where 1 is the poorest perceived quality and 5 is the best perceived quality. A Mean Opinion Score is determined by computing the arithmetic mean of all scores recorded from the results of a set of standardized tests where a number of listeners score the perceived audible quality of a series of prescribed test sentences read aloud by both male and female voices within a prescribed test environment, over the communications medium being tested. A Mean Opinion Score is a subjective measurement process, as listeners need to sit together in a quiet room and score call quality as they perceive it. Obtaining a Mean Opinion Score is time-consuming and expensive, as it requires involving multiple prospective or active users to accomplish the protocols as required by the standardized testing methods.
In voice over internet protocol (VoIP) telephony, a Mean Opinion Score provides a numerical indication of perceived quality of a received media after compression/decompression (codec) and/or transmission has taken place. Measurement applications for wireless, VoIP, fixed and codec telephony systems have been developed and are calculated based on performance of the IP network used within the system, as well as empirically assimilated for automated MOS results via implementation of ITU-T P.862.1, mapping of Perceptual Evaluation of Speech Quality (PESQ) scores to Mean Opinion Score (MOS) scale.
Perceptual Evaluation of Speech Quality (PESQ) is presented in ITU-T recommendation P.862, and comprises a test methodology for assessment of speech quality as experienced by users of telephony systems or networks. Specifically, PESQ was developed to standardize and automate Mean Opinion Score tests by employing algorithms to analyze speech signals. PESQ utilizes true voice samples as test signals; use of other, non-spoken audible signals, such as tones or noise, may yield unpredictable results. PESQ is a full-reference (FR) algorithm and analyzes speech signal sample-by-sample after a sequential alignment of corresponding excerpts of reference and test signal. PESQ may be applied to provide end-to-end (E2E) quality assessment scores for a network or for individual network components.
A full reference (FR) algorithm, such as PESQ, uses an established reference signal for comparison purposes. It can compare each sample of the reference signal (upstream end) to each corresponding sample of the degraded signal (downstream end). Full reference measurements provide a high level of accuracy and repeatability, but they may only be applied for dedicated tests in live networks, therefore, technicians, or more generally, users, must be available on both ends to initiate, receive and complete the testing and quality assessment of the live network and/or its components.
What is needed in the art is an automated electronic device which may be connected to a telephony network component or a telephony system in order to accommodate and perform Perceptual Evaluation of Speech Quality assessments in an imitated live scenario such that an estimated Mean Opinion Score may be produced for a telephony system without need for live user involvement on either the dispatching (upstream) end or the receiving (downstream) end.